1. Field of the Invention
The present invention relates generally to a touch pen, and more particularly, to a touch pen configured to directly input information to a portable terminal screen.
2. Description of the Related Art
Modern portable terminals such as navigation systems, Personal Data Assistants (PDAs), Motion Pictures Experts Group (MPEG)—Layer Audio 3 (MP3) players, Portable Multimedia Players (PMPs), electronic books, and tablet Personal Computers (PCs) are generally provided with a touch screen (also referred to as a touch panel). Inputting is executed by touching a keyboard or icons displayed on the touch screen by fingertip. However, as inter-icon spaces or icons become smaller, many malfunctions may be caused when a user touches the icons or keyboard with a fingertip.
For example, both a point adjacent to the intended touch point and the intended touch point are touched, or although the user has touched the intended touch point, a point adjacent to the touched position may be recognized first, causing a function which is not desired by the user to be executed.
In order to solve these problems, touch pens of various types are used. For example, a stylus is configured to press a touch screen to operate a keyboard or the like, and a conductive material or resonance frequency is configured to touch a desired position on the touch screen, thereby measuring a fluctuation of electrostatic capacity.
A constant pressure type touch pen, such as a stylus pen, continuously applies a constant pressure to the touch screen whenever the touch pen touches the touch panel. Accordingly, there is a problem of damage to the touch panel, which is frequently touched by the touch pan, and when the touch pen touches a damaged position on the touch panel, the touch is not recognized well or an error is produced. For this reason, there has been an increase in the use of more stable touch pens, such as the touch pen disclosed in Korean Unexamined Patent Publication No. 10-2009-0091631 published on Aug. 28, 2009 and entitled, Capacitive Touch Pen, which will now be described.
FIG. 1 illustrates an electromagnetic field distribution when a conventional touch pen with a resonance circuit vertically contacts a touch panel. Referring to FIG. 1, the touch pen 10, which uses a resonance circuit, includes a body 11 with a tip 12 adapted to contact a touch panel 20, a ferrite core 13, and a board (not shown) are provided inside of the body 11, in which a coil 14 is wound around the ferrite core 13. The components inside of the touch pen 10 including the ferrite core 13 wound with the coil 14 form a resonance circuit (not shown) that causes resonance at a frequency delivered from the touch panel 20. Accordingly, it is possible to obtain the positional information or writing pressure information of the touch pen 10 through a detected value transmitted or received between the touch panel 20 and the touch pen 10 using an induced electromotive force produced from the resonance circuit inside of the touch pen 10.
FIG. 2 illustrates an electromagnetic field distribution when the conventional touch pen with the resonance circuit slantingly contacts the touch screen, and FIG. 3 illustrates a touch point touched by the conventional touch pen, and an indicated state of the touch point when the touch pen with the resonance circuit slantingly contacts the touch panel.
Referring to FIGS. 2 and 3, when a user practically uses the touch pen 10, the user uses the touch pen 10 in a slanted state in relation to the touch panel 20, as illustrated in FIG. 2, rather than using the touch pen 10 in a vertically erected state in relation to the touch panel 20, as illustrated in FIG. 1. Thus, when used in this slanted state, the position of the induced electromotive force produced from the components inside of the touch pen 10 is adjacent to the touch panel 20. As such, the position of the central axis C of the electromagnetic field M produced due to the contact of the touch pen 10 is displaced to be spaced away to the slanted direction of the touch pen 10 from the contact point A of the touch pen 10, as illustrated in FIG. 2. Accordingly, although the tip 12 of the touch pen 10 contacts the position of point A on the touch panel 20, the central axis C of the electromagnetic field M is produced at the position of point B, and an indication produced when the tip 12 of the touch pen 10 contacts point B appears.
Thus, as illustrated in FIG. 3, the contact point A contacted by the touch pen 10 is not indicated but a contact to another point B adjacent to the contact point A is recognized, and point B is indicated at a position of the central axis C of the electromagnetic field. Accordingly, there arises a problem in that when the touch pen 10 is contacted to execute an icon at a desired position, such as the position of point A, another icon instead of the icon at the desired position is executed, such as an icon at the position of point B, thereby executing an undesired operation. In addition, when the user writes or draws a picture with the touch pen 10, it is difficult for the user to determine an intended position because the position contacted by the tip 12 of the touch pen 10 on the touch panel 20 and the position indicated on the touch panel 20 become disparate, thereby visually confusing the user.
Due to the error between the contact point A and the indication point B, a user cannot rely on the contact of the touch pen 10. Furthermore, due to the difference caused between the contact point A and the indication point B, the indication point B is obscured by the touch pen 10 or the user's hand, and the user inconveniently has to continuously confirm whether the touch pen 10 is correctly contacted.